Munc13-3 Superprimes Synaptic Vesicles at Granule Cell-to-Basket Cell Synapses in the Mouse Cerebellum
Munc13-3 Superprimes Synaptic Vesicles at Granule Cell-to-Basket Cell Synapses in the Mouse Cerebellum
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DOI：
10.1523/jneurosci.2060-14.2014
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发表时间：
2014-10-29
影响因子：
5.3
通讯作者：
Eilers, Jens
中科院分区：
文献类型：
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作者：
Ishiyama, Shimpei;Schmidt, Hartmut;Eilers, Jens
Munc 13 -3是一种突触前蛋白，参与小泡启动，在小脑颗粒细胞（GC）中强烈表达。缺乏Munc 13 -3的小鼠（Munc 13 -3（-/-））显示出增加的成对脉冲比（PPR），这导致了Munc 13 -3增加囊泡释放概率（p（r））的假设。在本研究中，我们分析了野生型和Munc 13 -3（-/-）小鼠急性小脑切片中GC和篮细胞之间的单一突触连接。从Munc 13 -3（-/-）GC记录的单一EPSC显示正常的动力学和突触潜伏期，但PPR和突触失败分数显著增加。量子分析表明，无论是单量子的电荷，也不二项式参数N的影响，由Munc 13 -3的损失，但Pr几乎减半Munc 13 -3（-/-）。既不突触前Ca 2+内流的影响删除Munc 13 -3也不容易释放的囊泡池的补充。然而，高浓度的EGTA导致EPSC的减少，其在Munc 13 -3（-/-）中显著更强。我们的结论是，Munc 13 -3是负责的分子和/或位置的“超启动”，大大增加了Ca 2+触发释放的功效的额外步骤。
Munc13-3 is a presynaptic protein implicated in vesicle priming that is strongly expressed in cerebellar granule cells (GCs). Mice deficient of Munc13-3 (Munc13-3(-/-)) show an increased paired-pulse ratio (PPR), which led to the hypothesis that Munc13-3 increases the release probability (p(r)) of vesicles. In the present study, we analyzed unitary synaptic connections between GCs and basket cells in acute cerebellar slices from wild-type and Munc13-3(-/-) mice. Unitary EPSCs recorded from Munc13-3(-/-) GCs showed normal kinetics and synaptic latency but a significantly increased PPR and fraction of synaptic failures. A quantal analysis revealed that neither the charge of single quanta nor the binominal parameter N were affected by loss of Munc13-3 but that pr was almost halved in Munc13-3(-/-). Neither presynaptic Ca2+ influx was affected by deletion of Munc13-3 nor replenishment of the readily releasable vesicle pool. However, a high concentration of EGTA led to a reduction in EPSCs that was significantly stronger in Munc13-3(-/-). We conclude that Munc13-3 is responsible for an additional step of molecular and/or positional "superpriming" that substantially increases the efficacy of Ca2+-triggered release.